Linear shaped charge unit



Jan. 12, 1965 Filed July a. 1962 H- T. ARMSTRONG LINEAR SHAPED CHARGE UNIT 2 Sheets-Sheet 1 HOMER 7'. ARMSTRONG INVENTOR.

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AGENT Jan. 12, 1965 H. T. ARMSTRONG 3,165,057

. LINEAR SHAPED CHARGE uurr Filed July 2, 1962 2' Sheets-Sheet 2 HOMER 7'. ARMSTRONG INVENTOR.

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AGENT United States Patent Ofl ice 3,165,057 LENEAR SHAPED CHARGE UNIT Home: T. Armstrong, Arlington, Tern, assignor to Ling- Terncovonght, Inc, Dallas, Tern, a corporation of Delaware Filed July 2, 1962, Ser. No. 206,900 2 Claims. (Cl. 102-24) This invention relates to explosive devices, and particularly to improved means for controlling the action and manner of application of the forces generated by the action of explosives. More particularly, the invention is concerned wtih preformed explosives so encased and of such physical configurations that the effective forces of their explosion are largely directed in pre-determined directions and may be utilized for cutting objects of differing mass or thickness or where the objects to be cut are on different planes requiring a plurality of directional cutting jets.

The term cutting is used herein as a more or less generic term to include the cutting, severing, piercing or slotting of objects. The objects referred to may include any materials such as metal, stone, wood, ore bodies or other earth formations generally.

The method of directing an explosive blast in a given direction, variously known as the cavity effec shapedcharge effect or Munro effect has been known and used for many years. Basically, this method requires that the explosive material be provided with a cavity facing in the direction to which the blast is to be directed. In order to achieve the most effective and concentrated blast, such cavity charges must be spaced from the work (standoff distance) at the time of detonation, and their efliciency is greatly increased if the cavity is provided with a liner, preferably of metal; the cavity liner and explosive in combination providing a highly effective jet cutting agent. The principles involved in the nature and proportioning of the charge, the shape of the cavity, the proportions of the liner, and the stand-off distance to achieve maximum penetration of the cutting jet have been thoroughly investigated and are well known to persons skilled in this art, and some examples of linear shaped charges are disclosed in US. Letters Patent Nos. 2,543,057; 2,513,233; 2,758,543 and 2,587,243. However, such linear shaped charges have heretofore contemplated only the cutting of objects of generally uniform thickness or density and in a single plane.

My invention contemplates a simply-formed linear shaped charge for cutting objects of differing thicknesses or density along the length of the linear shaped charge or the cutting of objects in more than one plane. It comprises an explosive-filled formable tubing member grooved to form an angular cavity along the length of the tubing, and providing, at positions where a greater concentration of explosive force is required, an explosive-filled concentric tubing member of greater cross-sectional area having a groove and cavity positioned contiguous to and in superimposed registry with the groove and cavity of the inner tubing member. It is contemplated that additional grooves may be formed in the larger tubing member so that they would present more than one explosive cavity facing in more than one direction toward objects to be cut.

An object of my invention is the provision of an improved linear shaped charge for producing cutting jets in a novel and effective manner.

Another object is the provision of an improved linear shaped charge adapted to produce cutting jets in more than one direction. I

Yet another object is to provide an improved linear shaped charge for cutting objects of different thicknesses or densities.

Other objects and advantages will become obvious from the following description when it is read in connection with the accompanying drawing, in which FIGURE 1 is an isometric view of a piece of smalldiameter tubing used for the basic tubular casing of my linear shaped charge;

FIGURE 2 is an isometric view of a piece of large diameter tubing used for the secondary tubular casing of my linear shaped charge;

FIGURES 35 are isometric views showing the tubular casings in simple dies for forming grooves in the tubing;

FIGURES 6 is an isometric View of my improved shaped charge;

FIGURES 7-9 are isometric views of modifications of my improved linear shaped charge; and

FIGURES 10-12 are illustrations exemplary of the uses to which the shaped charge units of FIGURES 6-9 may be put for the cutting of structural members.

Referring to the drawing, FIGURES l and 2 show tubular members 10 and '12 of differing cross-sectional areas used in my invention. The tubing is preferably of metal and I have used aluminum, copper or stainless steel tubing with good results but the tubing should be pliable enough to be grooved as hereinafter explained, and also pliable enough to permit its conformance to the line of a desired cut.

The smaller diameter tubing 10 is filled with a finegrain brisant explosive 11 such as cyclotrimethylenetrinitramine, commonly referred to as RDX or cyclonite, and the ends of the tubing are plugged with an inert sealing agent 34 such as wax or clay. A longitudinal groove is then formed in the tubing by'the use of adequate tooling, a simplified form of which is shown in FIGURE 3 in which 13a is a die base for supporting the tubing and 13b is a punch having an angular V-shaped edge 13c which is forced, under pressure, to deform the tubing and form a longitudinal groove therein defining a cavity. It will be understood, of course, that more elaborate tooling can be used. The angle of the V-shaped edge of punch 130 may be varied as desired and I have used punches having included angles of from 60 to but have found that a 90 angle works satisfactorily for most cutting operations. When the tubing is formed in the above manner the edges 15a and 15b of the tubing at the base of the grooved cavity 14 provide a satisfactory stand-off distance for the cavity, so that, upon explosion, the portion of the tubing lining the cavity, together with the explosive, combine to form an efiicient cutting jet. 7

Such a forming method is an extremely simple way of making a linear shaped charge with an efiicient cavity and stand-off distance. The pressure under which punch forms the groove in the tubing is important since such pressure packs the explosive charge in the reduced cross-sectional area of the grooved tubing. It has been found, by experimentation, that a pressure of around 40,000 lbs. per square inch on; the punch forms a satisfactory groove without unduly packing the explosive charge.

On occasion, it is required to cut structures having areas of differing densities or mass along the line of the desired cut such as local areas where there is more than one thickness of material to be cut, and FIGURES l0,

11 and 12 illustrate such conditions. To provide a greater explosive cutting force at such local areas I take a piece of tubing 12, similar to, but of larger diameter than, the basic tubing member 10, of sufficient length to cover the local'area to be cut, and groove it in tooling such as 13a, 13a and 13 as shown in FIGURE 4, this tooling being similarto that shown in FIGURE 3, but larger, to accommodate the larger size tubing. The piece of larger diameter tubing 12 is then sleeved over the smaller diameter tubing and positioned along its length Patentearan. 12, 1-965 so that it will coincide with the local heavy area to be cut. The apex of the groove 14 in the larger tubing is piaced contiguous with the apex of the groove a in the smalier tubing so that the cavities in each tubing are in superimposed registry and face in the same direction. The larger tubing is then filled with explosive 1i and its ends sealed with an inert substance 34. The inert sealant plug 34 in one end of the srnalier tubing is then removed and a primer detonator inserted within the tubing as shown in FIGURE 9, after which the tubing end is again plugged with sealant 34. It will now be seen that a compound linear shaped charge has been provided with additional explosive force at the area of the larger tubing to cut local structure of greater mass or density than the prime object to be cut by the explosive jet from the smaller diameter tubing member alone. in this arrangement it is not necessary to have a separate detonator in the large diameter tubing because the shock wave of the explosion in the smaller tubing member will detonate the explosive in the larger tubing member without having a separate detonator. In some installations it may be desirable to place the detonator in the larger tubing member.

As is illustrated in FEGURES 10, 11 and 12, there may be occasions where the cutting jet is desired to be directed in more than one direction, for instance, to out local structure such as the extending web and flanges of angles, brackets, hat sections or similar structures commonly used in metal construction. To provide multi-directional cu ting jets at local areas, I have modified the FIGURE 6 linear shaped charge as shown in FIGURES 7, 8 and 9 wherein, before the detonator is inserted in the smaller tubing, the larger tubing member may be provided with a secondary groove or cavity 16 to provide a second directional explosive cutting jet. The secondary grooves or cavities 16 may be formed by the tooling 13g, 1311, 131' and 131' shown in FIGURE 5, which is similar to the tooling shown in FIGURE 4 with the addition of a pointed raised portion 13j in the base section to accommodate the already formed groove in the tubing section. It will be understood that the punch 1311 may impress a secondary groove over the entire length of the large diam eter tubing section or selectively, by shorter punches, over oniy a portion of the length of the tubing section. it will also be understood that, while the secondary groove is shown in the drawing as being diametrically opposite the first groove, the raised portion 13 and/or punch 1311 of the tooling could be so arranged that the secondary groove would be at other circumferential positions.

In FIGURE 7, for an example, the second groove 16 is formed diametrically opposite to the first groove 14 in the larger tubing member so that the two cutting jets could sever the structure shown in FIGURE 11 along the line to be cut, whereby an explosive cutting jet would be directed from the register'mg cavities of both the smaller and larger tubing members to cut the double thickness of metal comprised of plate 19 and bracket flange 2t and also the lower part of bracket web 21, while a secondary explosive cutting jet would be directed upwardly from the secondary cavity in the larger tubing member to cut bracket flange 18 and the upper par-t of bracket web 21.

In FIGURE 8, a second groove 16 is formed only along an end portion of the length of the larger tubing member and this linear charge can be used to supply the two directional jet cutting action along a portion of its length, and a high force one-direction explosive jet cutting action along the remainder of its length as would be required to cut the structure shown in FIGURE 10. In this case the single direction, higher force, section of the compound linear charge unit would be positioned so that it would cut the double thickness of the plate 22 and bracket flange 23, while the two directional section of the compound linear charge unit would be positioned so that it would cut the bracket web 24, the plate 22 and the spaced flange 25.

FIGURE 9 shows a linear charge in which a second groove 16 has been impressed in the larger diameter tubing member in an intermediate portion only along the length of the larger tubing member and such a configuration could be used to cut the structure shown in FIGURE 12, wherein the two-directional central portion of the compound charge unit can be positioned to direct its cutting actions toward the adjacent plate 27 as well as the webs 23, 29 and the central portion 3% of hat section 26, while the one-direction higher-force end portions of the compound charge are positioned to direct their cutting actions toward the double thickness object comprised of plate 27 and hat section flange 31 at one end, and plate 27 and hat section flange 32 at the other end.

In use, the linear shaped charge is positioned contiguous to the object, or objects, to be cut along the path of the desired cut and can be lightly held in place by taping it to the object at longitudinally spaced distances with a pressure-sensitive tape 35, or other means, suflicient to maintain its position. Where structural members project from the member to be cut in the path of the cut line, holes such as 17 may be drilled in them through which the linear charge can be drawn. In positioning the linear charge in this manner, care is required to see that the cavities of the first and second tubular members are maintained in the desired positions facing the objects to be cut.

It will be evident from the above that my invent-ion provides a simply-formed linear shaped charge having a secondary or compound local explosive section selectively positioned along its length which may be formed to provide increased explosive jet cutting act-ion to augment the cutting action of the primary linear shaped charge at the local area or may be formed to provide multi-directional cutting jets at selected portions of the local area. It will also be evident that various modifications are possible in the arrangement and construction of my compound linear shaped charge unit without departing from the scope of the invention as delineated in the appended claims.

I claim:

1. A linear shaped charge unit comprising,

an explosive,

a first tubular rigid container having a first exterior groove that extends linearly along the outer surface thereof, said first container being filled with a quantity of said explosive that has been compacted as result of the formation of said first groove,

2. second tubular rigid container having a larger crosssection than said first container and being positioned to enclose a portion of the length of said first container, said second container having a second exterior groove that extends along the outer surface thereof, said second container being filled with said first filled container and with an additional quantity of said explosive that has been compacted as a result of the formation of said second groove,

said second groove being superimposed and aligned over the adjacent portion of said first groove for combining a cutting jet from each of said containers and directing the combined jet toward an object to be cut, and a detonator in contact with the explosive in at least one of said containers.

2. A linear shaped charge unit as claimed in claim 1 in which said second container has a third exterior groove that extends along the surface of said second container spaced apart from said second groove of said second container,

whereby, upon detonation, the explosive cutting actions will be in different radial directions from said second container according to the orientation of said grooves, the combined cutting action effective on a surface adjacent to said second groove that is superimposed over a portion of said first groove being greater than the cutting action on a surface adjacent said first groove that extends beyond said second groove, and also being greater than the cutting action on a surface adjacent said third groove.

References Cited by the Examiner UNITED STATES PATENTS 2,797,892 7/57. Ryan 102-24 x 2,972,948 .2/61 'Kray 10256 FOREIGN PATENTS 5 789,041 *1/58 Great Britain.

SAMUEL FEINBERG, Primary Examiner.

' ARTHUR M. HORTON, Examiner. 

1. A LINEAR SHAPED CHARGE UNIT COMPRISING, AN EXPLOSIVE, A FIRST TUBULAR RIGID CONTAINER HAVING A FIRST EXTERIOR GROOVE THAT EXTENDS LINEARLY ALONG THE OUTER SURFACE THEREOF, SAID FIRST CONTAINER BEING FILLED WITH A QUANTITY OF SAID EXPLOSIVE THAT HAS BEEN COMPACTED AS RESULT OF THE FORMATION OF SAID FIRST GROOVE, A SECOND TUBULAR RIGID CONTAINER HAVING A LARGER CROSSSECTION THAN SAID FIRST CONTAINER AND BEING POSITIONED TO ENCLOSE A PORTION OF THE LENGTH OF SAID FIRST CONTAINER, SAID SECOND CONTAINER HAVING A SECOND EXTERIOR GROOVE THE EXTENDS ALONG THE OUTER SURFACE THEREOF, SAID SECOND CONTAINER BEING FILLED WITH SAID FIRST FILLED CONTAINER AND WITH AN ADDITIONAL QUANTITY OF SAID EXPLOSIVE THAT HAS BEEN COMPACTED AS A RESULT OF THE FORMATION OF SAID SECOND GROOVE, SAID SECOND GROOVE BEING SUPERIMPOSED AND ALIGNED OVER THE ADJACENT PORTION OF SAID FIRST GROOVE FOR COMBINING A CUTTING JET FROM EACH OF SAID CONTAINERS AND DIRECTING THE COMBINED JET TOWARD AN OBJECT TO BE CUT, AND A DETONATOR IN CONTACT WITH THE EXPLOSIVE IN AT LEAST ONE OF SAID CONTAINRS. 